Verizon has announced it will sell Apple's iPhone 4 on 10 February, and a key issue for consumers is: Does popular devices cause the same network that the problem at AT & T? Although more than 73 million iPhones have been sold worldwide since the Apple Inc. smart phone introduced in mid-2007, U.S. carriers alone - AT & T - has passed the complaints from users about slow performance and dropped calls. Telephone, Verizon added to the list Tuesday, has a data-intensive features such as online game-playing and streaming that has been blamed for AT & T woes. Analysts have warned that if Verizon is not careful, it could be on the same defeat. "AT & T must pass through a little pain in order to understand what the demand from customers really look like," said Charles Golvin, a telecommunications analyst at Forrester Research Inc. "But Verizon has gone through a learning curve - the first from watching AT & T and The second of watching people in their own networks using data-intensive devices. " Verizon now covers an array list of supported Google's Android smart phone built by manufacturers such as Motorola, HTC and Samsung. Over the last yeark Android phone has proved tough competition for AT & T iPhone. AT & T has focused on what he said was a slower speed than the Verizon network. In November, the company released a research note that the network is 60% faster than Verizon. Verizon did not dispute the claim.